In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of achieving higher-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (see Non Patent Literature 1).
In LTE, as multi access schemes, an OFDMA (Orthogonal Frequency Division Multiple Access)-based system is adopted for the downlink and an SC-FDMA (Single Carrier Frequency Division Multiple Access)-based system is adopted for the uplink.
For the purposes of achieving further broadbandization and higher speed, successor systems to LTE are also under study, which are called , for example, LTE advanced or LTE enhancement, and specified in LTE Rel. 10/11 (LTE-A).
As duplex modes in radio communications of the LTE system and LTE-A system, there are FDD (Frequency Division Duplex) for dividing uplink (UL) and downlink (DL) by frequency and TDD (Time Division Duplex) for dividing uplink and downlink by time.
In TDD of the LTE system, there are defined UL-DL configurations #0 to #6 of which ratios between UL subframes and DL subframes in a radio frame are mutually different from each other (see FIG. 1). The user terminal performs communication based on any of the UL-DL configurations that is given by SIB1 (System Information Block Type1).
In LTE Rel. 12, which is a further successor system to LTE, study has been made of Dynamic TDD (or Rel. 12 eIMTA (enhanced Interference Management and Traffic Adaptation)) in which TDD frame configurations are dynamically switched in accordance with uplink and downlink traffics by dynamically switching existing UL-DL configurations.